transmission very slow to engage forward gears... - PeachParts Mercedes-Benz Forum

1lowdiesel · #1 02-10-2010, 02:50 PM

ok so i've read through about 20 threads with people having transmission issue s and they all seem to be based around shifting issues and nothing really direct the problem i'm having.

here is my issue, my car (83 300sd) was shifting fine up untill i "fixed" a vacuum line. the other day i was checking some things under the hood and found the vac line that goes to the trans was melted against the valve cover and was closed off on both ends. No big deal i'll just cut out the bad section and put a rubber hose in.

Now since i've done that the car is not wanting to get out of the hole. i can put it in gear and it'll just sit there or creep very very slowly forward. if i touch the gas it will basically go into neutral and just rev no matter how hard i hit the throttle. the only way it seems i can get it going is by rapping the throttle rapidly over and over, only then will the car start to grab and slowly take off. sometimes it will grab hard and go, other times it's got it's own mind and will come in and out of neutral. you can actually feel the trans grab then let go.

so far i've tried blocking off the line again the way it was but it didn't do anything. i've checked the fluid and it doesn't look or smell burnt. i'm not 100% familiar with the the Benz terminology so please if you can dumb it down for me. i haven't had a chance to check for vacuum yet but i'm thinking that is going to be my problem... i hope.

any help would be greatly appreciated.

kyle

here is a pic of my set up, as i couldn't find any good pics of my exact set up.

gyrzang · #2 02-10-2010, 03:40 PM

I am pretty sure the vacuum line that goes to the trans is to dampen the shift from gear to gear. Is the plastic adjust nut on valve cover set correctly? It goes down to trans on passenger side.

1lowdiesel · #3 02-10-2010, 04:14 PM

define correctly...

rrgrassi · #4 02-10-2010, 04:46 PM

You may want to look at a vacuum diagram. I see where the green damper is getting vacuum, but then where is it running? All I saw was blocked ports. The prior owner may have hacked it, and now you get to fix it.

Is the fluid level correct?

Vacuum does not have anything to do with the tranny engaging, but it does affect shift quality, while the bowden cable affects shift points based on throttle position.

1lowdiesel · #5 02-10-2010, 05:14 PM

ahh. well i just messed with the cable anyway and it didn't make a difference.

i actually blocked them off thinking that maybe when i "fixed" the line it caused the problem. i can feel vacuum at the junction block by the fuse box.

what gets me is that when you put it in reverse it clunks and starts moving.

i also tried running the small clear line that is in the lower left of this pic, directly to the line going to the trans and it didn't do anything either

rrgrassi · #6 02-10-2010, 05:27 PM

Is the tranny fluid level correct? It should be between the "hi and low" marks on the tranny dipstick.

compress ignite · #7 02-10-2010, 05:30 PM

Whose lower end is fitted to the Green Plastic Cylinder,which is fitted to the
Vacuum Control Valve (Underneath It),SHOULD be connected by Vacuum line
to your Transmission's Modulator Valve.(On the Driver's side of the Tranny)

The way it's shown in your pics , the Modulator Valve isn't getting any
Vacuum info from the engine.

Let's hope all you've gotta do is ADJUST the Bowden Cable and "Fix" the
hacked Modulator Vacuum Line.

I'll refer you to Stevebfl's tutorial on Tranny Adjustment:
http://www.peachparts.com/Wikka/TransVacTune

These two are also good:
http://www.peachparts.com/shopforum/showthread.php?p=100041

http://www.peachparts.com/shopforum/showthread.php?t=158216

And,And RRGrassi has the most important advice for you above.

1lowdiesel · #8 02-10-2010, 05:39 PM

yea fluid is good. a while back it started to slip too and the fluid was a little low. i put some stop slip in and it's been fine up until now. if anything it's a bit high now cause i put some more stop slip in.

i do understand that line goes to that Y and i did have it that way. i put the plugs back in there to simulate when it was busted and not getting vac to the trans.

now could driving the car with that line busted have caused something else internally to go bad?

funny too b/c it shifted perfect when the line was busted.

compress ignite · #9 02-10-2010, 06:26 PM

it "Shifted Perfect' when the line was busted.
It's all "Outa whack"
AND/OR been "Adjusted" so far outside the normal Parameters ,Same,Same.

I hate to approach this Turn...
The Tranny should still engage and shift (at some point) even with the
Modulator out of the system.

Me, I'd change the Fluid and Filter (Inspect the Pan for Debris and Swarf)
and Start from scratch on the Adjustments...
[You cannot successfully "Wing it" (AKA "Seat of Pants") the Tranny
Adjustment Procedures ... it's "A first then B then C, Etc.,Etc."]

1lowdiesel · #10 02-10-2010, 06:48 PM

i'm thinking that changing the fluid and filter are going to be my next step. unfortunately we're under about 2' of snow here so it's not going to be fun.

anyone thinking it could be the B2. seems that is a problem part with high mileage cars.

Hit Man X · #11 02-10-2010, 10:13 PM

Drop pan and replace filter also drain converter while in there, refill and see where that gets you. A plugged filter will reduce/severely limit line pressure.

It sounds like a B2 issue as the first and second gears use bands, which pretty much do not wear out unless burned. Typically reverse is first to go, then direct (4th), and then third.

B2 is a pain but not too hard.

1lowdiesel · #12 02-11-2010, 11:03 AM

thanks man. yea i would imagine line pressure would be cut way down with the filter clogged.

so you are thinking the B2 huh. i've been looking at pics of the B2 and it does look fun lol

konstan · #13 02-11-2010, 07:50 PM

Also, since you said you were missing fluid a while back, its important to find out where the fluid went... Check the trans. cooler lines. Cheap and easy to replace and they often leak.

layback40 · #14 02-11-2010, 08:36 PM

If you have been putting "stop slip" in, you may have other problems like burned clutches & bands. Why did you need it? Flairing? Taking the trans pan off may show more of what has happened.

1lowdiesel · #15 02-12-2010, 12:54 PM

i put it in there originally becasue it was leaking and causing it to slip taking off. put a bottle in and it was perfect.

now i''m on the hunt for a filter and a pan gasket. local parts store didn't have one. pep boys either.